1. Field of the Invention
The present invention relates to a magnetic recording medium or the like in a magnetic recording device.
2. Description of the Related Art
An increase in recording density is demanded for a magnetic recording device such as a hard disk device. One means for increasing recording density is decreasing magnetic spacing.
Magnetic spacing is defined by the distance from the surface of the magnetic recording transducer (hereafter also called transducer) to the top face of the magnetic layer of the magnetic recording medium, or to the half of the film thickness of the magnetic layer, and is a total of the thickness of the magnetic head protective layer (also called the “head protective layer” in this specification), the thickness of the magnetic head lubricant layer (also called the “head lubricant layer” in this specification), the flying height (also called “floating height”) of the transducer, the thickness of the magnetic recording medium lubricant layer (also called the “medium lubricant layer” in this specification), and the thickness of the magnetic recording medium protective layer (also called the “medium protective layer” in this specification) (in the latter case, the half of the film thickness of the magnetic layer is further added). The head lubricant layer may be omitted.
If the magnetic spacing is decreased by decreasing the distance between the transducer and the magnetic recording medium, the signal intensity and reproduction resolution increases at reproduction, and the recording magnetic field intensity and recording resolution increases at recording, which is an advantage (e.g. see Japanese Unexamined Patent Application Publication No. H9-219077 (paragraph No. 0003)).
Improvements (that is a decrease) of the magnetic spacing is approaching the limit. The major means for improving the magnetic spacing of a hard disk device has, for example, been decreasing the film thickness of the medium protective layer and decreasing the flying height of the transducer, but the flying height of the transducer is already about 10 nm, and can no longer be decreased if the unevenness on the surface of the magnetic recording medium is considered, because a further decrease of the flying height may cause contact of the transducer and the surface of the magnetic recording medium, which would result in damage to the transducer and the magnetic recording medium.
The medium protective layer has already reached about a 3 nm thickness, and it is difficult to decrease this further since the role of the medium protective layer is to prevent the corrosion of the magnetic recording medium while maintaining sufficient hardness for protecting the magnetic recording medium and the transducer in the event of both contacting. Therefore a decrease in the flying height of the transducer and a decrease in the film thickness of the medium protective layer are approaching the limit. This situation is the same for the head protective layer if the head protective layer is formed on the transducer.